wiring weirdness 2001 mercedes s430

Hi all,

I'm racking my brain and can't figure out what's wrong.  Was hoping *someone* here might be able to help me as it's driving me nuts!!!

The car/situation:

2001 Mercedes S430, has the Mercedes "COMAND" radio/nav/cassette/cd unit.

About a year ago, I installed a Parrot MK6100 bluetooth handsfree system, and also perma-wired my Garmin Nuvi.  For the Parrot, I ran the power wire to the Comand(radio) constant and switched power wires, and ran the Parrot's ground to radio ground. 

For the GPS, plugged the cigar lighter plug that came with it into a female cigar lighter socket, then wired those two wires to power and ground as appropriate.

*Everything* worked properly for one full year!  Starting the car caused the GPS to charge and the Parrot to work.  Shutting it off caused everything to shut down properly.

Last weekend, the GPS didn't fire up when I started the car.  I shut the car off and restarted, and the GPS was fine.  For the next 3 days, the GPS didn't power up at all.  This morning I manually turned it on (ran on its own internal battery) and it started to charge all by itself about 15 mins later.

When the GPS 'disconnected itself' from the car last weekend, so did the Parrot.  It has been completely dead since and has never powered up again.

I pulled the radio and checked all contacts and wiring.. they are good.  I had a completely new Parrot system intended for my other car, so I ended up swapping one part at a time till I had a completely new system in the car.  Still didn't work!!!!

Tested the Parrot power harness and it shows +12V on the constant, and +12V on the switched with the ignition on.  When I plug the connector into the Parrot, it clicks (as if powering on) and when I turn the key to accessory, the parrot clicks again.  When I shut the key off, it clicks once more.  This is all completely normal as if it's working, but still it doesn't fire up and there is nothing on the display!

My only thought was that the cold weather caused it (since the GPS fired up today after running the car for 15 mins) but that would be out of the question because I installed everything last Dec and drove through the entire winter with it, with no problem at all. 

Considering I swapped out the entire Parrot system and a brand new one is doing the same, it's definitely a problem with the car... but where?  The Comand radio works just fine, and everything is attached to the Comand wires.  Have checked all fuses for the Parrot and they are fine.  The GPS fuse is in the cigar lighter plug, so it's buried under the dash somewhere.  Not sure the GPS fuse is the problem, as it did work for 1/2 hour this morning just fine.

Next (final) steps before I tear my hair out:

-Pull the Comand (once more) and try wiring the Parrot unit to my cigar lighter.  I could use dig out the male Garmin cigar lighter plug from wherever I buried it, and try to plug it directly into the cigar lighter to see if a different circuit/fuse will make it work.

-Try my new Parrot on a spare 12V car battery I have, to see if it will fire up OK.  I'm sure it will, which will just confuse me more :)

Any help/thoughts/insights??? Would be MUCH appreciated!  I feel like a total idiot as this is probably something simple, I just can't figure it out!!!